Kew Water Hardness & Quality Report (2026)

Thames Water supplies Kew, the south-west London district in the London Borough of Richmond upon Thames — world-renowned home of the Royal Botanic Gardens at Kew Gardens, a UNESCO World Heritage Site and one of the world's greatest plant research institutions, set on the south bank of the Thames opposite the great arc of the Middlesex bank — from the River Thames and River Lee chalk-tributary blend in the south-west London Richmond distribution zone, treated at Lee Valley Water Treatment Works. At 269 mg/L (18.9°Clark), Kew's water is very hard — harder than typical Thames Hampton-zone communities west of London, reflecting a significant Lee Valley chalk-tributary contribution in the Thames Water Richmond distribution blend.

Kew lies in the Thames Water Richmond distribution zone where supply draws on a blend of the chalk-influenced Thames and a substantial Lee Valley chalk component, producing 269 mg/L with TDS 721 mg/L — very hard water notably harder than Hampton-zone outer west London communities (180–190 mg/L), consistent with the Richmond and outer south-west London supply sub-zones that draw a greater proportion from the chalk-dominant Lee Valley works for the south-west London distribution network.

At 269 mg/L, limescale is a persistent and significant household problem in Kew. Kettles should be descaled every two to three weeks. The combi-boiler needs a fitted scale inhibitor and annual professional servicing. Washing-up liquid requires generous quantities for adequate lather. Taps and shower heads develop substantial white chalk deposits within a week to ten days; a fortnightly descaling with white vinegar or a proprietary product keeps fittings in good condition. Kew's world-famous botanists may have celebrated the extraordinary mineral diversity of the plant kingdom — but every Kew household deals daily with just one very persistent mineral: the calcium chalk of the Lee Valley supply.